The aim of this paper is twofold. First, we want to examine whether and if so, to what extent, the concept of International Financial Reporting Standards (IFRS) meets the requirements of a Common Consolidated Corporate Tax Base (CCCTB) for the EU-wide activities of multinationals as proposed by the European Commission. Second, we estimate the consequences on the effective levels of company tax burdens in selected EU member states if IFRS are considered as a tool for defining the tax base. Our analysis reveals that IFRS could provide elements of a common and harmonised European tax base in certain areas. In particular, tax accounting still has to follow the realisation principle. Therefore, IFRS “fair value-accounting” cannot be adopted for tax purposes. A transition to tax accounting on the basis of IFRS has only minor effects on the effective tax burdens of companies.